PARIS — In the worst traffic disaster in 33 years in France, a truck collided head-on with a bus carrying elderly people on a sightseeing excursion in the southwest on Friday morning, killing at least 43 people and injuring eight others, officials said. Residents of the small town where most of the victims lived mourned the loss of nearly an entire generation.

The crash took place around 7:30 a.m. near the town of Puisseguin, close to the city of Libourne and east of Bordeaux. According to the authorities, a truck used to transport wood swerved at a curve in a rural road and struck the bus, causing both vehicles to burst into flames.

The bus passengers, members of a senior citizens’ club in Petit-Palais-et-Cornemps, about five miles north of Puisseguin, were headed first to a tasting of the neighboring region’s famous cured hams at a shop 120 miles away. Sylvie Milhard, whose uncle died in the crash, said, “It’s a whole generation that is lost.”

Xavier Sublett, the mayor of Puisseguin, said the accident happened on a sharp bend in the road, several hundred feet from the town. “The bus was hit by a truck that was coming the opposite way and that missed a tight turn,” he said in a phone interview, adding that the road was “pretty and very picturesque” but not in poor condition.

At a news conference in Libourne on Friday evening, Christophe Auger, the public prosecutor there, said the exact death toll was not certain because it was still unclear whether everybody scheduled to go on the excursion had actually done so.

The truck driver was also killed. The authorities announced that they had found the body of a 3-year-old boy — the driver’s son — in the truck’s cab. Of the eight people who were injured, two sustained head injuries and two others had burns, while four were slightly hurt.

Prime Minister Manuel Valls, speaking to reporters in Puisseguin, called the accident “horrifying” and added, “We have not seen such a catastrophe on our roads for over 30 years.”

Interior Minister Bernard Cazeneuve also headed to the scene, as did Alain Juppé, a former prime minister who is now the mayor of Bordeaux.

The bus was traveling to La Maison du Jambon de Bayonne in Arzacq-Arraziguet, a store and museum devoted to the region’s cured hams, according to Bertrand Ecomard, the head of the museum.

Col. Ghislain Réty of the Gironde gendarmerie told reporters at the scene that 250 officers had been deployed and that it was too early to say what had caused the accident.

He said the bus driver had acted “heroically” by helping several people get out of the bus.

“He gave us a few details; he is extremely shocked,” Colonel Réty said of the driver. “So these elements are going to be reconfirmed and corroborated, especially with the technical evidence that will be taken from the scene.”

He added that one of the biggest questions was why the bus had caught fire so quickly. “For now, I do not have any leads,” he said.

At the news conference, Mr. Auger, the prosecutor, said the bus driver gave statements to the police suggesting that the truck driver might have been driving outside his lane. But he said the first priority was to positively identify the victims.

A police colonel at the news conference said identification could take up to three weeks, suggesting that the bodies were badly burned.

“At this stage of the investigation, it is obviously impossible and very premature to consider any kind of criminal responsibility,” said Mr. Auger, adding that the police would speak with witnesses, look at driving conditions on Friday and analyze both vehicles to determine how the crash had happened and how the passengers were killed.

Aerial footage on French television showed the charred frames of the bus and the truck, with the fronts of both vehicles apparently slammed against each other, and the truck’s cab turned to its side.

Video

Mayor Xavier Sublett of the village of Puisseguin and Prime Minister Manuel Valls of France spoke on Friday after a bus and a truck collided in southwestern France, killing at least 43 people.CreditCreditJean-Pierre Muller/Agence France-Presse — Getty Images

A car that was behind the bus stopped after the accident, and its driver broke one of the bus’s rear windows to free several passengers, Colonel Réty said.

The bodies of the victims were being brought to a police laboratory in Bordeaux, but a place of grieving was set up near Puisseguin Town Hall, Mayor Sublett said.

In a phone interview from Petit-Palais-et-Cornemps, Ms. Milhard, 60, said her uncle Michel Rogerie had died in the crash. Mr. Rogerie, 84, was a former mayor of the town and the current president of its senior citizens’ club.

Pascal Romain, a council member in Petit-Palais-et-Cornemps, said, “It is a real tragedy because it is a very small town, and everybody knows one another.”

Ms. Milhard expressed frustration that residents of Petit-Palais-et-Cornemps had received little information until the early afternoon, when the town hall released the list of survivors.

“It was horrible, everybody was crying,” she said. “With my husband, we could have been part of this club, I am 60 and he is 61. Several of the passengers were friends from school, we grew up together.”

Gilles Clion, 57, the owner of a restaurant in the town, said the town was in a state of shock.

“Their cars are still parked on the town square, they had all gathered there to take the bus,” he said in a telephone interview. “I recognize some of the license plates, and I know that there will be people I know among the dead.”

Mr. Clion said that his mother, sister and brother-in-law had all planned to join the outing but had canceled at the last minute.

The Road Safety Association said the disaster was the worst road accident in France since one that killed 53 people, including 44 children, near Beaune, the wine capital of Burgundy, in July 1982.